The present invention relates to the bulk material handling technology, particularly to the separation of the commercial part of the material and removal of the pollutant part of the material from the air, and may find various industrial and agricultural applications, e.g. handling of the grain products.
The bulk material as dwelt upon herein consists of the solid particles differing by mass, size, shape and optionally constituting the substances. Some particles meet the commercial requirements (the commercial part), whereas the other particles are the pollutants (the pollutant part), and both the commercial part and the pollutant part may in turn include several various fractions differing in particle parameter ranges.
The existing bulk material separators not only separate the commercial particles into fractions, but also remove the pollutant particles from the air by directing them to the special tanks, hereinafter the residue collection chambers.
Multiple devices are known that both simply purify the bulk materials from the pollutants and separate the commercial part of the bulk material removing the pollutant part of the material from the air simultaneously.
By the principle of the operation such devices may be divided into the screen type which separate fractions on screens according to particle size, and the aerodynamic type where the particle flow is blown with the air and the fractions are separated according to their aerodynamic characteristics.
The aerodynamic devices are divided by the air stream passage type into the direct-flow type where an air blower takes the external air and then exhausts the air purified to the various degrees into the environment, and the recirculation type where at least part of the air is recycled to the air blower inlet.
The present invention relates just to the aerodynamic recirculating separator of the bulk materials.
In general, in the aerodynamic devices where a gas stream is created, the particle moving in the gas stream is acted as effected by gravity and under the influence of force developed by the air motion (hereinafter the air effective force) which is proportional to the square of flow velocity and air density at given point and depends on a particle maximum section area. If the gravity force is substantially larger than the air effective force, the latter may only deflect the particles from their vertical direction. If the air effective force is substantially larger than the gravity force, the particles soar in the air without descending. The particles are characterized by the minimum soaring velocity in the given air stream, i.e. the minimum air stream velocity at which particles of a certain shape and mass begin soaring.
The separation process, i.e. the separation of the commercial-size particles into fractions, takes place at the separation chamber and consists in development of the air stream by the blower which velocity is substantially lower than the soaring velocity of the commercial-size particles and, eventually, of some heavy fractions of the pollutant particles, but this velocity is sufficient to deflect the commercial-size particles of a target fraction from the vertical direction by prescribed distance under the free fall from the specified height and exceeds the soaring velocity of light fractions.
It must be noted that the air blower capacity and the air stream parameters (density, velocity and shape) at the separation chamber must be defined exclusively by the parameters of the bulk material to be purified, namely, by size, mass and shape distribution of the commercial particles. More particularly, the main requirement in formation of the air stream coming into the separation chamber is the necessary deflection degree of the useful, i.e. commercial, particles under their fall from the loading hopper so that they got to the discharge channels. Meanwhile, the particles which did not get to the discharge channels must be carried by the air stream away from the separation chamber and removed somewhere else. In this connection, for instance, the cyclones are not advisable for the polluted air cleaning in the recirculating separators, as they require much higher the air stream velocity and/or air blower capacity than it is necessary for the aerodynamic separation per se.
Another important aspect of the recirculating separator is the fact that a high degree of air purification must be ensured within one recurring cycle, so that as few as possible pollutant particles returned to the separation chamber via the air blower, so that they did not deposit on the air blower movable parts and on the air duct walls, thus hampering the device operation and deteriorating its efficiency and the other operational parameters.
The closest prior art solution to that presented in this invention is described in Russian Federation Patent No 2194580, publication date 26 Dec. 2002. The grain cleaner for cleaning and fractionation of the grain materials according to this patent comprises the receptacle, the closed air system with a cross-flow fan, the loading window, the air duct and the residue collection chamber, wherein the receptacle includes the feeder, the cross-flow fan pressure nozzle is mated via the controllable feeder lip screen to the inclined air separator channel having on its top wall the loading window and in the bottom part opposite to the loading window the reception tanks for grain material separation products with the rotary planes fixed on hinges to their walls, whereas the cross-flow fan sucking window is mated to the feeder via the lip screen and to the dischargers of the grain material separation product reception tanks via the dust deflecting channel formed by the wall congruent to the fan shell wall.
The disadvantages of this prior art are the high air pollution at the cross-flow fan (air blower) inlet which increases a probability of the non-commercial material particle sticking to the fan movable parts, its imbalance and eventual failure. Especially hazardous in this respect are the sticky bulk materials, e. g. the sunflower seeds.
Then, in this cleaner device the dust is sucked off from the separation product reception tanks along the narrow dust deflecting channel mated with the fan. On a par with the increased air pollution degree at the fan inlet and the unsatisfactory cleaning at the outlet of the separation product reception tanks, it also adds to the environment pollution, as an excess air coming into the dust deflecting channel is exhausted to the environment, mostly with the commercial fractions of material through the separation product reception tanks and/or through the feeder.